Ion Diffusion Properties Research Articles

Electrolytic ion diffusion properties and their effects on charge storage potentials of pseudocapacitive Co3O4 electrode film

Electrolytic ion diffusion properties and their effects on charge storage potentials of pseudocapacitive Co3O4 electrode film

Gate-Controlled Potassium Intercalation and Superconductivity in Molybdenum Disulfide.

Intercalation of guest ions into a van der Waals (vdW) gap in layered materials is a powerful route to create novel material phases and functionalities. Ionic gating is a technique to control the motions and configuration of ions for both intercalation and surface electrostatic doping. The advance of ionic gating enables the in situ probe of dynamics of ion diffusion, carrier doping, and transport properties. Here we performed in situ resistivity and Raman experiments on the potassium ion (K+) intercalation of single-crystal MoS2 and constructed a temperature-carrier density phase diagram. The K+-intercalation induces a structural transition from the prismatically coordinated phase to the octahedrally coordinated phase, where anisotropic three-dimensional superconductivity and a possible charge density wave state were observed. The present ionic gating offers a comprehensive view of the intercalated phases and proves that the electrostatically induced superconductivity is distinct from that in the intercalated phase.

Understanding the influence of sodium chloride concentration on ion diffusion in charged polymers

Previous observations made on sulfonated polysulfones equilibrated with solutions of increasing salinity, where salt diffusion coefficients increase concurrently with reductions in water content driven by osmotic de-swelling, are currently unexplained. To further explain the molecular underpinnings of these observations, we characterized the influence of external salt solution concentration on the average salt and ion diffusion properties of two sulfonated polymers: a model cross-linked material (XLAMPS) and a series of sulfonated polysulfones (HQ:BP – XX). Analysis of the average salt and co- and counter-ion diffusion coefficients in these polymers suggest that the increase in charge screening (of electrostatic interactions between anionic sulfonate groups and co-ions) that occurs with increasing salinity affects the salt diffusion coefficients of sulfonated polysulfone in a manner that is different from what would be expected based on changes in water content alone and from what was observed for XLAMPS. Free volume theory describes the influence of these electrostatic effects on salt diffusion using a parameter related to the characteristic free volume element size necessary for diffusion. The results and analysis suggest that charge screening reduces the characteristic free volume element size necessary for diffusion in sulfonated polysulfone, which provides an explanation for the observed increase in average salt diffusion coefficients with increased salinity.

Ultrafast Knock-Off Li+ Diffusion and Subtle Structural Evolution of Li5V3O8 Anode in Lithium-Ion Batteries.

Li5V3O8, a lithiation product derived from the LiV3O8 cathode, has emerged as a promising intercalation-type anode material, boasting a theoretical capacity of 256 mA h g-1. Through a comprehensive combination of experimental and theoretical approaches, we demonstrate its capability to intercalate a substantial amount of Li+ at extremely high rates. Experimental findings reveal that Li5V3O8 exhibits outstanding high-rate capability (with a specific capacity of 152 mA h g-1, 60% of the theoretical capacity at 40 C) and exceptional cyclability (with a capacity retention of 80% after 11,000 cycles at 20 C). The structural changes in Li5V3O8 during the lithiation/delithiation cycles are subtle and reversible. First-principles calculations highlight a knock-off mechanism in Li+ diffusion within Li5V3O8, with an estimated energy barrier ranging from 0.16 to 0.38 eV, considerably lower than that of a direct hopping mechanism (0.62-1.44 eV). These ultrafast ion diffusion properties are attributed to interlock interactions among interstitial tetrahedral Li+ and neighboring octahedral lattice Li+, facilitating long-distance and chain-like Li+ diffusion. This study not only introduces an influential vanadium-based anode material with practical implications for fast-charging lithium-ion batteries but also provides fundamental insights into solid state Li+ diffusion kinetics.

Machine Learning-Accelerated First-Principles Study of Atomic Configuration and Ionic Diffusion in Li10GeP2S12 Solid Electrolyte.

The solid electrolyte Li10GeP2S12 (LGPS) plays a crucial role in the development of all-solid-state batteries and has been widely studied both experimentally and theoretically. The properties of solid electrolytes, such as thermodynamic stability, conductivity, band gap, and more, are closely related to their ground-state structures. However, the presence of site-disordered co-occupancy of Ge/P and defective fractional occupancy of lithium ions results in an exceptionally large number of possible atomic configurations (structures). Currently, the electrostatic energy criterion is widely used to screen favorable candidates and reduce computational costs in first-principles calculations. In this study, we employ the machine learning- and active-learning-based LAsou method, in combination with first-principles calculations, to efficiently predict the most stable configuration of LGPS as reported in the literature. Then, we investigate the diffusion properties of Li ions within the temperature range of 500-900 K using ab initio molecular dynamics. The results demonstrate that the atomic configurations with different skeletons and Li ion distributions significantly affect the Li ions' diffusion. Moreover, the results also suggest that the LAsou method is valuable for refining experimental crystal structures, accelerating theoretical calculations, and facilitating the design of new solid electrolyte materials in the future.

Ag@Co/Zn N‐Doped Carbon as Antibacterial Oxygen Reduction Catalysts for Microbial Fuel Cells

Biofouling of air cathode surface decreases the electricity generation performance of membrane‐free microbial fuel cells (MFCs). Ag@Co/Zn N‐doped carbon (Ag@Co/Zn‐NC) is designed as an antibacterial oxygen reduction reaction (ORR) catalyst to inhibit biofouling on the cathode surface. The Co/Zn‐NC active component promotes ORR catalytic activity through the advantages of well‐distributed Co nanoparticles and numerous active sites. Superficial Ag nanoparticles act as antibacterial active species to inhibit bacterial proliferation and suppress biofilm growth. Ag@Co/Zn‐NC catalyst prevents bacterial adhesion and biofilm formation, effectively preventing excessive biofouling on the cathode surface. The antibacterial catalyst maintains a high catalytic activity and good ion diffusion properties without the adverse effects of biofouling, resulting in enhanced ORR durability of the air cathode. The assembled MFCs achieve high electricity generation during long‐term cyclic operation. The maximum power density retention percentage (82.6%) is higher than that of Co/Zn‐NC MFC (65.3%) and Pt/C MFC (52.4%) after continuous operation for 1200 h. Excellent operational durability is revealed for the air‐cathode MFCs assembled with the antibacterial ORR catalyst during the cyclic process. The novelty of this study is that the design of antibacterial catalysts inhibits the excessive growth of the cathode biofilm to improve the cyclic electricity generation performance of MFCs.

Theoretical investigation of Mo2C and Mo2CO2 as anodes for sodium/magnesium-ion batteries

Due to the rapid evolution of the global electronic product industry, the limited availability of lithium resources has prompted extensive research into alternative metal ion batteries that can substitute for lithium batteries. The exceptional potentiality for MXenes as electrode materials in energy storage batteries is demonstrated by excellent conductivity, expansive surface area, and mechanical strength. The performance of Na and Mg on Mo2C and Mo2CO2 monolayers have been investigated employing first-principles calculations, including geometry configurations, electronic structures, ion diffusion properties, open-circuit voltages, and theoretical specific capacities. The conductivity of stable anodes is superior both before and after ion adsorption. Additionally, the formation energies of Na/Mg on the monolayer are negative, indicating a strong binding between metal atoms and the substrate. The migration energy barriers of Na and Mg on Mo2C are estimated to be 0.017 eV and 0.070 eV, respectively, suggesting a significant level of mobility and reversibility for Mo2C. The predicted range of average open-circuit voltages for Na/Mg-ion battery anodes is approximately 0.05–1.00 V in the case of Mo2C and Mo2CO2. The highest concentrations of Na and Mg atoms on Mo2C and Mo2CO2 are achieved through multilayer adsorption up to Mo2CNa3.3, Mo2CMg2, Mo2CO2Na3.3, and Mo2CO2Mg1.8, resulting in corresponding theoretical capacities of 438, 526, 379 and 411 mA·h/g, respectively. In conclusion, the outstanding electrochemical performance of Mo2C and Mo2CO2 anode materials in sodium-ion batteries (SIBs) and magnesium-ion batteries (MIBs) has prompted the exploration of other MXenes electrodes with advantageous characteristics for ion battery applications, contributing to the advancement of renewable energy technology.

First-principles study of slag impurity doped Na2Ti3O7 as anode material for Na-ion batteries

Na2Ti3O7 (NTO) has attracted significant attention as a promising anode material for sodium-ion batteries (SIBs). However, its practical electrochemical performance is hindered by its inherently low electronic conductivity. To address this limitation, researchers have turned to elemental doping as an effective strategy to enhance the conductivity of NTO electrodes. Interestingly, the process of purifying titanium for NTO synthesis often yields Al and Ca impurities, which can be harnessed as cost-effective dopants. In this study, we employ first-principles calculations to conduct a comprehensive investigation into the structural, electronic, and sodium ion diffusion properties of NTO when doped with Al and Ca, either individually or in combination. Doping system structure has good stability. Our findings reveal that both Al or Ca single-doping Our findings reveal that all the Al and Ca single-doping, and AlCa co-doping transform NTO from semiconducting into metallicity. Notably, the sodium ion migration barriers for Ca single-doping greatly decrease (0.13 eV) compared with that of pristine NTO (0.23 eV), indicating fast ion transport. The insights gained from our research hold promise for the development of cost-effective multi-component anode materials for SIBs.

In Situ Phase Transformation to form MoO3−MoS2 Heterostructure with Enhanced Printable Sodium Ion Storage

AbstractMolybdenum trioxide (MoO3) possesses high energy density but often suffers from poor electrical conductivity and limited cycling stability when used as a sodium‐ion battery (SIB) anode. To address these issues, the construction of （Molybdenum trioxide‐Molybdenum disulfide）MoO3‐MoS2 heterostructures has proven effective in enhancing electronic conductivity, ion diffusion properties, and structural stability. Guided by the density functional theory (DFT) calculations, which predict favorable Na+ diffusion and adsorption properties, nanorod‐like MoO3‐MoS2 heterostructures are synthesized using a two‐step method. Benefiting from the synergistic effects of the heterostructure and nanosized morphology, the resulting MoO3‐MoS2 electrode exhibits outstanding rate performance (316 mA h g−1 at 10 A g−1) and long‐lasting cycling stability (286 mA h g−1 after 2300 cycles at 5 A g−1) as an SIB anode. In situ XRD measurements reveal that the ultrahigh specific capacity of MoO3‐MoS2 is attributed to the synergistic intercalation‐conversion storage of MoO3 and MoS2. In the pursuit of meeting commercialization requirements, electrodes with adjustable mass loading are also prepared using 3D printing, showcasing the high areal capacity characteristics of the SIBs. This study not only provides theoretical insights into expanding the use of heterojunction materials as SIB anodes but also demonstrates the significant potential for creating high‐energy‐density and cost‐effective SIBs.

Theoretical calculations and simulations power the design of inorganic solid-state electrolytes.

Using solid-state electrolytes (SSEs) to build batteries helps improve the safety and lifespan of batteries, making it crucial to deeply understand the fundamental physical and chemical properties of SSEs. Theoretical calculations based on modern quantum chemical methods and molecular simulation techniques can explore the relationship between the structure and performance of SSEs at the atomic and molecular levels. In this review, we first comprehensively introduce theoretical methods used to assess the stability of SSEs, including mechanical, phase, and electrochemical stability, and summarize the significant progress achieved through these methods. Next, we outline the methods for calculating ion diffusion properties and discuss the advantages and limitations of these methods by combining the diffusion behaviors and mechanisms of ions in the bulk phase, grain boundaries, and electrode-solid electrolyte interfaces. Finally, we summarize the latest research progress in the discovery of high-quality SSEs through high-throughput screening and machine learning and discuss the application prospects of a new mode that incorporates machine learning into high-throughput screening.

Oxygen dynamic exchange and diffusion characteristics of ZnO nanorods from 17O MAS NMR.

Interactions of ZnO nanorods with water and the dynamic migration characteristic of surface oxygen species are important in controlling its structure and catalytic properties. Here, we apply 17O solid-state NMR spectroscopy to investigate the interactions, as well as oxygen ion diffusion properties of ZnO nanorods under different conditions.

Investigation of Chloride Diffusion into Concrete with Joint

The passive layer shielding the steel reinforcement from corrosion can be attacked by the chloride ions that permeate through the chloride ions that permeate through the pores in the concrete when it is in solution. This paper aims to explore the investigation of chloride diffusion into concrete with joint. Three exposure conditions were taken into consideration in chloride ion diffusion experiments in order to examine the impact of exposure conditions on the chloride ion diffusion property: long-term immersion in a static sodium chloride solution, long-term immersion in a circulating sodium chloride solution, and dry–wet cycles in a circulating sodium chloride solution. According to experimental findings, the age of erosion increased the chloride ion content at a particular depth. Furthermore, concrete subjected to dry-wet cycles of the circulating sodium chloride solution had slightly higher chloride ion content than concrete immersed in the solution for an extended period of time. Fick's second law served as the foundation for the empirical equations that were developed by fitting experimental data to determine the chloride content and diffusion coefficient at the concrete's surface, as well as the correlation coefficient values for various exposure scenarios. The calculation formula's greater applicability was confirmed by comparison with the experiment results. The chloride ion content could be predicted and examined using this method for various exposure scenarios.

Hollow Bowl NiS2 @polyaniline Conductive Linker/Graphene Conductive Network: A Triple Composite for High-Performance Supercapacitor Applications.

The achievement of the outstanding theoretical capacitance of nickel sulfide (NiS2 ) is challenging due to its low conductivity, slow electrochemical kinetics, and poor structural stability. In this study, we utilize polyaniline (PANI) as a linker to anchor the NiS2 with a hollow bowl-like structure, uniformly dispersed at the surface of graphene oxide (GO)(NiS2 @15PG). The presence of PANI provides growth sites, resulting in a uniform and dense arrangement of NiS2 . This morphological modulation of NiS2 increases the contact area between the active material to electrolyte. Additionally, PANI effectively connects NiS2 with the conductive network of GO, which advances the electrical conductivity and ion diffusion properties. As a result, the Rct (charge transfer resistance) and Zw (Warburg impedance) of NiS2 @15PG decrease by 82.61 % and 66.76 % respectively. This unique structure confers NiS2 @15PG with high specific capacitance (536.13 C g-1 at 1 A g-1 ) and excellent multiplicative property of 60.93 % at 20 A g-1 . The assembled NiS2 @15PG//YP-50 supercapacitors (HSC) demonstrates an energy density (13.09 Wh kg-1 ) at a high-power density (16 kW kg-1 ). The capacity retention after 10,000 cycles at 5 A g-1 is 86.59 %, indicating its significant potential for practical applications.

Indium doping: An effective route to optimize the electrochemical performance of LiFePO4 cathode material

This study aimed to develop In-doped LiFePO4 cathode materials for lithium ion power batteries in electric vehicles that meet the requirements of both fast acceleration and long-term reversible charge-discharge stability. We focused on investigating the role of indium doping in enhancing high-rate capability. Density functional theory (DFT) calculations revealed that successful substitution of In at Fe site exhibits distinct features for both LiFe1-xInxPO4 and Fe1-xInxPO4. The results showed that the presence of In in unlithiated Fe1-xInxPO4 can lower the diffusion energy barrier of lithium ions. On the other hand, the introduction of In in lithiated LiFe1-xInxPO4 creates an impurity energy band at the Fermi energy level, which enhances electron conductivity of the active material. Experimental data demonstrated that with 2% In doping, the 2% In3+-LFP/C electrode delivers 160 mAh g−1 at 0.1C, and 150 mAh g−1 at 1C (with excellent retention rate of 98% after 700 cycles). Additionally, the In-doped electrode provided higher discharge capacity at high-rates (5C and 10C) due to improved electron conductivity and lithium ion diffusion properties. These findings prove that indium doping is an effective approach to reinforcing the electrochemical capabilities of high-rate LiFePO4 cathode material for lithium storage.

A Novel Na4MnCr(PO4)2F3 Cathode with High Energy Density for Sodium-Ion Batteries.

Na3V2(PO4)2F3 (NVPF) is a representative cathode material of sodium-ion batteries (SIBs) due to its high working voltage and high structural stability. However, its specific capacity is limited to the reversible inserting and extracting of two sodium ions per formula unit, which hampers the improvement of its energy density. In this study, we propose a new NASICON-type Na4MnCr(PO4)2F3 (NMCPF) cathode and systematically investigate its key properties using first-principles calculations. NMCPF exhibits the ability to extract/insert three sodium ions per formula unit, resulting in a high specific capacity of 180.34 mAh/g, and demonstrates three-electron redox reactions involving three redox couples of Mn2+/3+ (3.05 V), Mn3+/4+ (4.11 V), and Cr3+/4+ (4.64 V). Consequently, its energy density can reach 709.33 Wh/kg. In addition, NMCPF exhibits a small volume change of 8.2% during the charging/discharging process and sodium ion diffusion properties comparable to those of NVPF. This study demonstrates the potential of NMCPF as a promising cathode material with high energy density for SIBs.

Machine learning molecular dynamics simulation identifying weakly negative effect of polyanion rotation on Li-ion migration

Understanding the physical picture of Li ion transport in the current ionic conductors is quite essential to further develop lithium superionic conductors for solid-state batteries. The traditional practice of directly extrapolating room temperature ion diffusion properties from the high-temperature (>600 K) ab initio molecular dynamics simulations (AIMD) simulations by the Arrhenius assumption unavoidably cause some deviations. Fortunately, the ultralong-time molecular dynamics simulation based on the machine-learning interatomic potentials (MLMD) is a more suitable tool to probe into ion diffusion events at low temperatures and simultaneously keeps the accuracy at the density functional theory level. Herein, by the low-temperature MLMD simulations, the non-linear Arrhenius behavior of Li ion was found for Li3ErCl6, which is the main reason for the traditional AIMD simulation overestimating its ionic conductivity. The 1μs MLMD simulations capture polyanion rotation events in Li7P3S11 at room temperature, in which four [PS4]3− tetrahedra belonging to a part of the longer-chain [P2S7]4− group are noticed with remarkable rotational motions, while the isolated group [PS4]3− does not rotate. However, no polyanion rotation is observed in Li10GeP2S12, β-Li3PS4, Li3ErCl6, and Li3YBr6 at 300 K during 1μs simulation time. Additionally, the ultralong-time MLMD simulations demonstrate that not only there is no paddle-wheel effect in the crystalline Li7P3S11 at room temperature, but also the rotational [PS4]3− polyanion groups have weakly negative impacts on the overall Li ion diffusion. The ultralong-time MLMD simulations deepen our understanding of the relationship between the polyanion rotation and cation diffusion in ionic conductors at room environments.

Effect of Metakaolin on the Diffusion Properties of Chloride Ions in Cement Mortar under the Coupling Effect of Multiple Factors in Marine Environment

To address the problem of chloride ion transport in cement concrete in marine environment, this study investigates the effect of metakaolin dosage on the chloride ion diffusion resistance of mortar and its mechanism by testing the chloride ion binding capacity and microstructure of mortar under the coupling effect of chlorine salt-sulfate-carbonation multiple factors. The results show that the coupling of sulfate or carbonation reduces chloride ion transport to some extent compared with single chlorine salt attack, while the three-factor coupled environment promotes free chloride ion diffusion. This is because the products of calcium alumina, gypsum, and calcium carbonate grow together and compete with each other to form more large capillaries; thus, accelerating the diffusion of chloride ions in cement mortar. Metakaolin, due to its higher pozzolanic activity, increases the monocarbon aluminate content in the erosion products, promotes F-salt generation, and increases the Al/Si ratio, which strengthens the binding ability of C-S-H gel to chloride ions, so the free chloride ion concentration inside the specimens doped with metakaolin is lower. In particular, the three-factor coupled environment has less 0.05–10 μm capillary pore content and higher F-salt stability in the specimens, which has the strongest effect on chloride ion curing, and the free chloride ion concentration integral in M-SCCl is reduced by nearly 30% compared with MF-SCCl and F-SCCl.

Brownian Motion Simulation for Estimating Chloride Diffusivity of Cement Paste

Chloride ion diffusion properties are important factors that affect the durability of cementitious materials. Researchers have conducted much exploration in this field, both experimentally and theoretically. Numerical simulation techniques have been greatly improved as theoretical methods and testing techniques have been updated. Researchers have modeled cement particles mostly as circular shapes, simulated the diffusion of chloride ions, and derived chloride ion diffusion coefficients in two-dimensional models. In this paper, a three-dimensional random walk method based on Brownian motion is employed to evaluate the chloride ion diffusivity of cement paste with the use of numerical simulation techniques. Unlike previous simplified two-dimensional or three-dimensional models with restricted walks, this is a true three-dimensional simulation technique that can visually represent the cement hydration process and the diffusion behavior of chloride ions in cement paste. During the simulation, the cement particles were reduced to spheres, which were randomly distributed in a simulation cell with periodic boundary conditions. Brownian particles were then dropped into the cell and permanently captured if their initial position in the gel fell. Otherwise, a sphere tangential to the nearest cement particle was constructed, with the initial position as the center. Then, the Brownian particles randomly jumped to the surface of this sphere. The process was repeated to derive the average arrival time. In addition, the diffusion coefficient of chloride ions was deduced. The effectiveness of the method was also tentatively confirmed by the experimental data.

Research progress of two-dimensional antimonene in energy storage and conversion.

Since the first proposal of antimonene in 2015, extensive research attention has been drawn to its application in energy storage and conversion because of its excellent layered structure and fast ion diffusion properties. However, in contrast to the revolutionary expansion of antimonene-based energy devices, reviews on this topic that summarize and further guide the design of 2D antimonene for energy storage and conversion are rare. In this review, the structure, physicochemical properties, and popular synthesis approaches of antimonene are first summarised. Specifically, the rational design and application of antimonene in energy storage and conversion such as electrochemical batteries and supercapacitors, electrocatalytic hydrogen evolution reaction, electrocatalytic oxygen evolution reaction, electrocatalytic carbon dioxide reduction, photocatalytic reduction of organic pollution, photocatalytic reduction of carbon dioxide (CO2), solar cells and photovoltaic devices are outlined. Finally, opportunities and challenges are presented to further advance the development and application of antimonene in energy conversion and storage.

Construction of three-dimensional carbon materials-based conductive bonding network in flexible supercapacitor electrodes

High-performance supercapacitors are widely studied, but few works have paid attention to the optimization of conductive bonding networks in the electrode to improve its electrochemical performance. Herein, a rationally designed three-dimensional (3D) conductive bonding network consisting of one-dimensional carboxylated carbon nanotubes (CNT-COOH) and two-dimensional reduced holey graphene oxide (rHGO) is introduced to porous carbon nanofiber/ultra-thin MnO2 nanosheets (PCNF/U-MnO2) electrode through vacuum filtration. The CNT-COOH/rHGO network endows the electrode with desired electron transport and ion diffusion properties for its advantages in 3D structures, conductivity and electrolyte wettability, which promote efficient use of PCNF/U-MnO2 active materials. Thus, PCNF/U-MnO2 in the electrode with CNT-COOH/rHGO network shows better capacitive performance than that of traditionally fabricated electrode with PTFE and acetylene black. Besides, CNT-COOH/rHGO network is conducive to structural stability of PCNF/U-MnO2 electrode, and it obtains a capacitance retention of 87% even after 4500 cycles. Then, an asymmetric supercapacitor with PCNF/U-MnO2 cathode and N, B-doped PCNFs anode has been assembled, which exhibits good flexibility using LiCl/PVA hydrogel as electrolyte and has a high energy density of 45 Wh kg−1 at a power density of 540.8 W kg−1. The strategy of CNT-COOH/rHGO network construction can be an effective and promising way beneficial to high-performance supercapacitor fabrication.